Oil burning apparatus



Nov. 6, 1934. F. A. HEATH 1,979,465

om BURNING APPARATUS Original Filed Feb. l0, 1928 wir 0,00*@

ATT, A m95, ym.

Patented Nov. 6, 1934 '1,919,465 OIL -BURNING APPARATUS l Forrest A. Heath, Upper Montclair, N171. I

Application-February 10,' 192s, serial Nmzsaz'zo Renewed December 5,- 1930 es claims. (ci. 15a- 4) A My present invention concerns oil burning ap' paratus of the class in which metered, and more or less mixed oil and air are sprayed, preferably centrifugally above a refractory hearth #that closes in the lower end of a .lire box and more speciflcally to apparatushaving the oil projecting means and the hearth organized and operating in such combination that in normal full operation as well 'as at starting, the flame line or region where active combustion is precipitated is 1ominate in a vertical impingeinent wall of reG brick or the like, adapted to afford a catalytic surface to precipitate combustion at the periphery.

after it gets highly heated in normal running. This impingement wall extends upward tothe highest horizontal level towhich the oil can be projected by the projecting apparatus, so that most of the projected oil impnges thereon. Another feature is a collecting gutter or groove at the baseof this wall, of cross sectionsuiiicient to hold all of the uni'gnited oil that can collect during the starting period.4 Preferably, Ythis peripheral gutter is a pronounced groove,l deep enough so that the' exposed top surface of the oil collected therein is of small area. Another feature cooperating well with the collecting gutter, but which may be sufficient in itself, is to provide for an out drainage of the hearth downward from the oil projector to the periphery; Preferably, the upper surface is sloped so that it will be close to but substantially out of range of the trajectory of the lowest part of the projected oil. is used, it necessarily forms a collecting annulus or gutter at, the base of the above described impact wall, so that incertain cases any more pronounced groove may be dispensed with.

From the above, it will be evident that while in many cases, particularly in re boxes of small diameter, thegroove may he useful with a hearth having a horizontal upper surface or even with My pres- Where such down slope hearth- ,in the collecting groove, in combination with an the down slopeoutwardly is capable of use without the groove, the down slope plus the pro- `nounced groove mutuallyvcooperate to produce the best results. In such combination, the outward down slope tends to -keep the .hearth free from impingement of unignited oil and facilitates outward drainage of any that does impinge, while the groove tends -to minimize the exposed surface of the oil collected therein.

Another novel feature of special utility in connection with a hearth that has an upper surface which does not drain by gravity toward the center, is vsetting the air 'and oil projector close to the center ofthe hearth so that the projected air sweeps the surface of the hearth while the oil projector remains high enough so that in normal full ,operation the projected oil cannot impinge on the hearth. When the air is thus .discharged over a hearth inwhich the upper surface is unobstructed and approximately parallel with the air draft, the` under surface ofthe air ,draft tends to follow the upper surface o f the hearth, thereby minimizing tendency of the air I to eddy back and ow reversely toward the center of the hearth, as is commonly the case, where the fan delivers theair at a level very substantially above that of the hearth, as in all prior apparatus where the path 'of the projected oil lies above the hearth and combustion is precipitated by impact of the air and oil upon a peripheral ignition Wall.

As a result, I am able to start the oil projector byvprojecting' only the amount of oil necessary for normal running, yet I accumulate at the pe-I riphery where it is to be ignited, an amplesupply of oil, -in even. less time than would be possible by an over-supply of oil projected uponthe usual' up-slope or horizontal hearth which does not have any peripheral gutter. Thus the oil is concentrated at. the desired ignition point so that it 95 is readily ignited. Moreover, after it is ignited, the excess oil volatilizes gradually from the sur;

.face downward. There is no large area of oil ony ignition torch..v .Another feature of my invention 'is a small,

continuously flowing pilot jet projecting upward ignition torch adapted, when turned on, to dis charge in igniting relation to the constantly burning pilot. The above and other features of my inventio will be more evident from the following descrip- Fig. 1 is a plan view of the hearth and burner, the surrounding fire box and water leg being as 6 shown in horizontal section;

Fig. 1a is an enlarged sectional detail showing more clearly and fully the fan and draft arrangements of the burner head; and

Fig. 2 is a vertical section on the broken line 2 2, Fig. 1. y

The furnace to be heated is shown in Fig. 2 as including a support annulus 1, closing in a space f which may be approximately the same as the ash pit space of an ordinary coal fire furnace. This supports the furnace which may be of any desired construction, the essential parts shown in Fig. 2 being the wall 2 closing in the ilre box and an outer wall 3 affording an interspace 4 for the water or air to be heated or boiled, as the case may be. An annular ledge 5 supports a plate or metal hearth pan 6, which in turn supports a refractory hearth 7 through which projects a burner, more or less diagrammatically indicated at A.

The hearth is formed at its periphery with the vertical ignition wall 8 having at the base thereof an oil collecting gutter, in this case a semi-cylindrical groove 9, into which project the pilot flame nozzles 10, 10. The ignition torches 11, 11 are in such position that when the gas' is turned on, the jets are each ignited by a continuously discharging pilot 10.

Various examples of oil and air projectors suitable for my purpose are now well known. One is the oil projector invented by Homer A. Tiffany, for which application for Letters Patent has been made, Ser. No. 355,688 led April 17, 1929, and another is set forth in my application Ser. No. 47,709. filed August 3rd, 1925, which `has resulted in Patent No. 1,707,474, issued April 2, 1929.

The oil is centrifugally discharged in an extremely fine spray or vapor through nozzles 12, supplied through a head 13 mounted on vertical shaft 14 which is an extension of an armature shaft of an electric motor contained in the casing A. This motor is of the usual construction and rotates the head at the usual high speed to project the oil from the nozzles 12, 12, in a trajectory, the upper and lower regions of which are indicated in a general way by the dotted lines X and Y, respectively. 'Ihe head carries fan blades 15 creating a powerful draft below the trajectory of the oil as suggested by the arrow Z. As shown in Figures 2 and 1a, there are ten or a dozen fan blades 15 carried by the under` face of the head 13. These constitute a large volume fan tending to create a vacuum in the interior space a. 'Ihe four nozzles 12 constitute another fan creating suction at e, and through annular passage d this suction takes eifect in the same space that the fan 15 draws from. The air inlet to this space a is through a slot b communicating with the ash pit. The cross section of this slot may be adjustably decreased or increased by vertical slide c. Thus, the many blades 15 and the four nozzles 12 constitute two fans drawing in parallel from the same source. The/respective suction effects oi' these two fans are very nearly the same,

but the amount of air delivered through l2 is much smaller than delivered through 15, because 7c the ow section of the 'four little nozzles is very through a suitable interior nozzle not shownl Centrifugal force causes a film of this oil from trough e to creep up the walls and ultimately to be thrown oif as a ne spray projected from the rear lips of the four nozzles 12. Centrifugal force also causes a. relatively small volume of air to be projected through these nozzles 12 while a much larger volume of air is being projected by the fan blades 15. The nozzles project substantially above the plane of the top plate 13 of the rotor. Consequently, said plate, together with the-upwardly projecting surfaces of the nozzles constitutes in effect a third fan whereby hot products of combustion are projected in the same horizontal plane with spray. The projected products of combustion and the air enveloping the spray lose velocity more quickly than thev spray, so that the spray tends to cut through the paths of the former. Thus the composite draft produced by the nozzles consists of a mixture of hot products of combustion, spray and a small percentage of air. When this composite mixture strikes the periphery of the hearth, the spray is further atomized and mixed with the primary air and gas and also with the air from the fan blades. These easily ignite, at starting, and when the apparatus is in full operation so that the refractory impact surfaces are at high heat, the combustion at the periphery is substantially perfect.

As shown in Figure 2, the rotary head is set very close to the hearth so that air discharged therefrom sweeps the surface of the hearth from the center outward, as indicated by the arrows Z, thus maintaining a smoothly flowing draft of air between the hearth surface and the projected oil. This is a great improvement over the arrangement shown in my prior Patent 1,707,474, and now commonly practiced in the art. In such cases, the peripheral ignition wall is much higher than the center of the hearth so that when the head is set high enough to throw oil against said wall, the fan is so high that the air from the under surface of the draft discharged thereby eddies backward toward the head instead of sweeping the surface of the hearth outward from the center to circumference. 'I'he oil and air supplies to the burner, as also the means for metering the same, form no part of my present invention and are not shown. Similarly, the means for continuously supplying gas to the pilot nozzles 1Q and intermittently supplying gas to the ignition torches 11 may be of any known or usual construction and are not shown. 'I'he important features are that the pilot nozzles 10 project above the highest level at which oil can collect in the groove 9, when the ordinary control apparatus required by the fire underwriters, is employed; also the ignition torch nozzles 1l are located inside the circumference of the collecting groove and the flame therefrom impinges obliquely upon the ignition wall, tending to drive the flame obliquely into the groove and around the wall, preferably in the same direction of rotation that the rotary head tends to rotate the body of air or gas within the fire box. n

If desired, supplemental air may be admitted through the hearth by nozzles 17, 17, which also discharge toward the ignition wall obliquely in the same direction as the ignition torches.

I have discovered by many experiments that an outward down slope for the hearth of approximately y2 inch to the foot is suflicient to keep the upper surface below the trajectory of the oil, even when the diameter of the fire box is a maximum. As a specic illustration of preferred construction, I may note that an 8-inch rotary head 12, 13, may be utilized for fire boxes of widely varying diameter simply by varying the metering of the oil and gas, a uniform running speed of, say, 1700 revolutions per minute being maintained for all sizes of furnace and all de grecs of heat. Where such a head is used in a fire box having a hearth only 24 inches in diameter, the oil only has to be thrown 8 inches. In such a case, a slight down slope to the hearth is desirable, although the distance is so short that all of the oil may be discharged with certainty against the ignition wall, regardless of whether the upper surface of the hearth is horizontal or is slightly sloping in either direction. For such small diameters, a collecting groove alone is amply sufficient for my purpose without the slope. With greater diameters, the outward down slope is progressively of greater importance, but for all sizesof hearth up to, say, 78 inches in diameter, the standard outward down slope of 1/2 inch to the foot is sufficient. The collecting depression may be a relatively shallow gutter, but I prefer a semi-cylindrical groove an inch or more in diameter.

The operation of the above apparatus'may., be described as follows:

The pilot jets, 10, are small and are continuously supplied with gas suflicient to ignite the jet from ignition torch 11, whenever the gas is turned on. The usual controls are employed whereby power is supplied to' rotate the head 13 to deliver a predetermined metered supply of oil along the lines X, Y and air or air and hot gas, as indicated by the arrow Z, and also to turn on the gas through ignition torch 1l. The ignition torch is immediately lighted by the pilot light and the oil projected against ignition wall 8 collects in groove 9. The maximum exposed surface of oil is therefore practically limited to the area of said ignition wall'and the upper surface area of the oil in groove 9. All of the oil being concentrated in the ignition region, the ignition torches quickly ignite the oil around the entire periphery, but, as before noted, such ignition does not bring into play any increased oil surface, because by my present invention there is little if any smearing or collecting of oil on the upper surfaces of the hearth. Consequently, the igniting operation is quick and uniformly progressive until the entire periphery flames and the controls usually employed for such purposes turn off the ignition torch 11 whenever ignition is fully established.

It will be noted that the pilot light may be and frequently does cease to be flaming when the oil is being rapidly vaporized and burned in close proximity thereto. 'I'his is no disadvantage because the amount of gas escaping is small and is burned along with the oil vapor so long as I normal operation continues. The important point eral impingement wall preferably follows theiire box wall in the relation indicated in cross section in Fig. 2, although it is often desirable to have it cut across the ext-'renie angles of the corners. The object in all cases is that the zone in which the active combustion is precipitated may be close enough so that the rising flame will hug the surface of the water leg.

- I claim:

1. -Apparatus of the class described. including a, fire box, a refractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer and a fan operating to maintain an outwardly flowing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of discharge of the o'il spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory impact wall of a height suflicient to intercept substantially all of the oil projected by the projecting means and having its upper surface sloping downwardly toward its periphery, and terminating in an oil-tight, oil-collecting gutter adjacent the base of said ignition wall.

2. Apparatus of the class described, including a re box, a refractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer and a fan operating to maintain an outwardly owing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having its upper surface in the form of a frustum of a flat cone draining outwardly toward the periphery and having a peripheral oil collecting gutter adjacent the base of said ignition wall.

3. Apparatus of the class described, including a fire box, airefractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer andal fan operating to maintain an outwardly fiowing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of the discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, re

fractory ignition wall of a height sufficient to intercept substantially all of the oil projected by the projecting means and having a peripheral o'l collecting gutter; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly adjacent said wall and an ignition torch located nearer the center and adapted to discharge in a direction to be' when the gas is turned ignited by said pilot light 4. Apparatus of the class described, including a nre box, a refractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer anda fan operating to maintain an outwardly flowing draft of air between the ol spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of dischargei of the oil spray, all designedA and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory ignition wall of a height sufficient to intercept substantially all of the oil 4projected by the projecting means and having a peripheral oil collecting gutter; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly through the bottom of said gutter and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on.

5. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal' oil sprayer and a fan operating to maintain an outwardly flowing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardlyl extending, refractory ignition wall of a height suflicient to int ercept substantially all of the oil projected by the projecting means and having its upper surface sloping downwardly toward its periphery; in combination with a continuously burning pilot light ma'ntained by a nozzle projecting upwardly adjacent said wall and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when -tliegasistumedon.

6. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer and a fan :operating to maintain an outwardly flowing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having its upper surface sloping downwardly toward its periphery and having a peripheral oil collecting gutter; in combination with a continuously burning pilot light -maintained by a nozzle .projecting upwardly 'through the bottom of said gutter and an ignition torch located nearer the center and adaptedtodischargeinadirectiontobeignited by said pilot light when the gas is turned on.

1. Apparatus of the class described, including a nre box, a refractory hearth closing in the bot tom thereof, and a rotary power driven head comprising a centrifugal oil sprayer and-a fan operating to maintain an outwardly flowing draft of air between the oil spray and thehearth, said hearth having a substantially unobstructed upper surface lyingbelow the level of discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth;

- said. hearth having adjacent its periphery an upwardly extending, refractory impact wall of a height suflicientto intercept substantially all of the oil projected by the projecting means and having its upper surface sloping downwardly toward its periphery and having a peripheral oil collecting gutter adjacent the base of said igni'- tion wall.

8. Apparatus of the class described, including a nre box, a refractory hearth closing inthe bottom thereof, and a rotary power driven head comprising a centrifugal oil sprayer and a fan the oil projected by the projecting means and having its upper surface sloping downwardly toward its periphery and having a peripheral oil collecting gutter; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly adjacent said wall through the bottom of said gutter and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on.

9. Apparatus of the classdescribed, including a fire box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent Athe periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory ignition wall of a height sumcient to intercept substantially all of the oil projected by the projecting means and having a peripheral oil collecting gutter; in combination with afcontinuously burning pilot light maintained by a nozzle projecting upwardly adjacent said wall and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said wall.

10. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory ignition wall of a height sufficient to intercept substantially all of the oil projected by the projecting means and having a peripheral oil collecting gutter; in combination with a continuously burning pilot light maintained bya nozzle projectingk upwardly adjacent saidwall and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned' on and to discharge obliquely along said wall and into said gutter. f l

1l. Apparatus of the class described, including a firebox, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory ignition wall of a' height sufficient to intercept substantially all of the oil projected by the projecting means and having a peripheral oil collectingy gutter; in combination with a continuously' burning pilot light main tained by a nozzle projecting upwardly adjacent said wall and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said gutter in the direction of rotation of said projector.

12. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector -discharging horizontallyv above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of thehearth; said los ' hearth having adjacent its periphery an upwardly extending, refractory ignition wall of a height sufficient to intercept substantially all 'of the oil projected by the projecting means and having its upper surface sloping downwardly toward the periphery; in combination with a continuouslyv burning pilot light maintained by a nozzle projecting upwardly adjacent said wall and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said gutter in the direction of rotation of said projector.

13. Apparatus yof the class described, including a re box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and al1( projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having its upper surface sloping downwardly toward its periphery and having/a peripheral oil collecting gutter; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly through the bottom of said gutter and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said gutter.

14. Apparatus of the class described, including a re box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having its upper surface sloping downwardly toward its periphery andhaving a peripheral oil collecting gutter; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said gutter.

I15. Apparatus of the class described, including a re box, a refractory hearth closing in the bottom thereof, and a centrifugal oil and air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery .of the hearth; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly, and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said periphery.

16. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, and a centrifugal oil andv air projector discharging horizontally above the hearth, said projector and hearth being of the type designed and operating to initiate combustion adjacent the periphery of the hearth; in combination with a continuously burning pilot light maintained by a nozzle projecting upwardly and an ignition torch located nearer the center and adapted to discharge in a direction to be ignited by said pilot light when the gas is turned on and to discharge obliquely along said periphery, together with an air inlet conduit through the hearth also adapted to discharge obliquely along said periphery in the same direction as said torch, said, direction being the same as the direction of rotation of said projector.

17. Apparatus of the class described, including a iire box, a refractory hearth closing in the bottom thereof, and a rotary head embodying a centrifugal oil sprayer and a fan operating to maintain an outwardly flowing draft of air between the oil spray and the hearth, said hearth having a substantially unobstructed upper surface lying below the level of discharge of the oil spray, all designed and operating to initiate combustion adjacent the periphery of the hearth; said hearth having adjacent its periphery an upwardly extending, refractory, ignition wall of a height sufficient-to intercept substantially all of the oil projected by the projecting means; and a peripheral oil collecting gutter adjacent the base of said ignition wall and lying below the eveltof said unobstructed upper surface of the ear h.

18. Apparatus of the class described, including a furnace, a hearth closing in the bottoml there-` of, a power driven centrifugal projector discharging air and oil horizontally, adjacent the upper surface of the hearth, said hearth having a burner portion adjacent its periphery, all designed and operating to initiate combustion in a peripheral zone at the location of said burner portion, the latter being formed with elements having upwardly extending, inwardly presented surfaces adapted to intercept the path of the projected oil and air and deflect them upwardly while vaporizing and producing a homogenizing effect on said oil and air; said parts being formed and arranged to afford an oil-tight oil collecting depression below the inwardly presented surface of the burner portion and below the level of the upper surface of the hearth, into which excess unvaporized oil owsby gravity from said upwardly extending inwardly presented surfaces of the burner portion.

19. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, a power driven rotary head provided with centrifugal oil spraying means and with a centrifugal air projecting fan, both discharging above the level of the hearth, said hearthv having refractory -ignition surfaces projecting upwardly adjacent its periphery, designed and located so as to intercept practically all of the projected oil spray; the fan and hearth being designed and arranged so that the under surface of the draft as `it leaves the fan sweeps the central portion of the hearth; and the upper surface of said hearth from the central portion outward toward the ignition surfaces being substantially uniform and unobstructed and sloping downward toward its periphery so as to afford a guide for and to be swept by the under surface of said air draft, thereby minimizing tendency to downward eddying and reverse flow of air from said under surface of the air draft toward the projector; and meansl for regulating the amount of air supplied to the fan; all designed arid operating to initiate combustion adjacent the periphery of the hearth.

20. Apparatus of the class described, including a fire box, a refractory hearth closing in the bottom thereof, a power driven rotary head provided with centrifugal oil spraying means and with a centrifugal air projecting fan, both discharging above the level of the hearth, said hearth having refractory impact surfaces adjacent its periphery, designed and located so as to intercept practically all ofthe projected oil spray and having an oil collecting gutter adjacent the base thereof; the fan and hearth being designed and arranged so that the under surface of the draft as it leaves the fan tends to sweep the upper surface of the central portion of the hearth; and said upper surface of the hearth from the central portion outward toward'the impact surfaces being sloped so that surplus oil drains outward from the center and so as to afford a uniform unobstructed guide surface swept by the undersurface of said draft, until the air reaches a peripheral zone where mixing with the oil is to be eected and combustion precipitated.

21. Apparatus of the class described, including a furnace affording a combustion'chamber, a hearth closingin the bottom of said chamber, said hearth being providedwith a central opening and an upwardly extending peripheral wall;

a power driven centrifugal projector projecting through said opening and arranged to afford a central annular inletfor an air draft, said projector having a head discharging oil and pro-- jecting the air draft approximately horizontally adjacent the upper surface of the hearth, said upper surface of the hearth having a slight outward and downward slope so as to be approximately parallel with the air draft projected by the head, and so as to drain oil toward the periphery of the hearth; all designed and operating to initiate combustion in an annular zone adjacent said peripheral wall.

22. Apparatus of the class described, including a furnace affording a combustion chamber, a hearth closing in the bottom of said chamber and `provided with a central opening. a power driven .centrifugal projector projecting through said opening and arranged to afford a central annular inlet for an air draft, saidprojector having a head discharging oil and projecting the air draft approximately horizontally adjacent the upper surface of the hearth; said upper surface of the hearth having a slight slope outward and downward from the head so as to be approximately parallel with the air draft projected by the head, and so as to drain oil toward the periphery of the hearth, in combination with an annular refractory element adjacent the furnace wall formed with inwardly presented impact surfaces disposed in the path of said loil and air to deect the same while vaporizing the oil and producing a homogenizing effect on said oil and air; and all designed and operating to initiate combustion in an annular zone adjacent vsaid annular refractory element. y

23. Apparatus of the class described, incl a rebox, a refractory hearth closing in the bottom thereof and a power driven rotary head comprising a centrifugal oil sprayer and a fan operating to maintain an outwardly flowing draft of air and oil spray, said hearth having a substantially unobstructed upper surface close to but below the level of discharge of the oil spray. and having adjacent its periphery an .upwardly extending refractory impact wall in the path of oil and air projected by the projecting means,Y

said upper surface of the hearth sloping downwardly toward its periphery and terminating in an 'oil-tight, oil-collecting annulus adjacent the base of said wall.

FORREST A. HEATH. 

